Contact lenses require frequent cleaning in order to remove deposits, the source of which is generally tear fluid. In addition to cleaning it is necessary to disinfect contact lenses to reduce the risk of infection. A common method of disinfecting contact lenses is to contact them with a three percent solution of hydrogen peroxide.
Prior art methods for carrying out the disinfecting process is first to clean and rinse the lenses and then to immerse them in an aqueous three percent solution of hydrogen peroxide for about 10 minutes. The lens is then treated for about 10 minutes to reduce residual hydrogen peroxide absorbed therein to a level which is non-toxic and not irritating to the eye. A prior art method for reducing residual hydrogen peroxide comprises chemical reduction by immersing the lens in an aqueous neutralizing solution followed by rinsing with isotonic saline. While neutralization has been accomplished in numerous ways in the prior art, one approach is to place the lenses in a container of saline solution having a plastic disc coated with catalytic platinum for about four hours. Other methods used for neutralizing residual peroxide include immersion of the lens in an aqueous isotonic saline containing catalase or thiosulfate, bisulfite and pyruvate salts.
British patent number 2,144,875A (British '875) discloses a process for the oxidative cleansing of contact lenses which is similar to that utilized in cleansing dentures. An oxidative cleansing solution is prepared using a solid material which gives chemical release of hydrogen peroxide. Illustrative examples of solid materials giving chemical release of hydrogen peroxide include percarbonates, persulfates, perborates, peroxyhydrates and other per salts of alkali metals and other anions. In one embodiment the solid material is mixed with anhydrous citric acid, polyvinylpyrrolidone and powdered sodium lauryl sulfate. The mixture is tabletted by compression in a conventional tabletting equipment.
British patent number 1,221,038 (British '038) discloses an effervescent medicinal tablet which comprises adipic acid and sodium bicarbonate. An alleged advantage of the use of adipic acid is that no lubricant is required in the tabletting process.
U.S. Pat. No. 4,414,127 discloses a method of utilizing a transition metal catalyzed peroxide solution to cleanse contact lenses. The preferred metal is copper. While the peroxide is generally provided in a solution form it can be made available as a tablet or powder. The hydrogen peroxide source can be a hydrogen peroxide solution, urea peroxide, sodium percarbonate or sodium perborate. The solution contains an imadazoline surfactant or a cocohydrolized animal protein anionic surfactant. While the concentration of hydrogen peroxide in solution is disclosed to encompass the range 0.1 to 15% by weight/volume. The preferred range is 0.5 to 10% (w/v). Most preferably, the peroxide concentration is 1%.
U.S. Pat. No. 4,401,582, discloses a method for ambient temperature or cold disinfection of soft contact lenses utilizing ascorbic acid for killing bacteria.
A method for disinfecting contact lenses is disclosed wherein an ene-diol composition is utilized in conjunction with copper ion. See for example U.S. Pat. Nos. 4,490,389; 4,581,472 and 4,581,379. The preferred ene-diols are dihydroxyfumaric acid, dihydroxymaleic acid, reductic acid and ascorbic acid.
U.S. Pat. No. 4,312,833, discloses a sterilizing solution for disinfecting contact lenses comprising (a) an alkali metal of formic acid, and (b) an iodophor selected from the group consisting of complexes of iodine with hydrophilic polymer and non-ionic surface active agent.